<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS的属性</title>
    <style type="text/css">
        h1{color: #ff0000;}
        div.dd{
            width: 300px;
            height: 300px;
            border: 1px solid #ff0000;
            margin: 20px;
            float: left;
        }
        div.aa{
            width: 300px;
            height: 300px;
            border: 1px solid chartreuse;
            /*margin: 20px;*/
        }
    </style>
</head>
<body>
<h1>CSS的属性：颜色</h1>

<div class="dd"></div>
<div class="dd"></div>
<div class="dd"></div>
<div class="dd"></div>
<div class="aa"></div>
</body>
</html>